Natural ivory is a material prized by many because of its distinguishing characteristics. It is relatively soft and characterized by a unique striped coloring which ages distinctively. The ivory may be carved and polished so as to form smooth decorative surfaces. Natural ivory also has a relatively high thermal conductivity, such that it remains cool to the touch. Further, it is a porous material, capable of absorbing liquids. These last two features are especially desirable for concert pianists and other musical performers, whom require cool, dry instrument keys even after long periods of heated, sweaty contact with the keys during performances.
However, the source for natural ivory, elephant tusks, is becoming increasingly more scarce and therefore difficult to obtain. Firstly, the world-wide population of elephants is rapidly diminishing due to the widespread killing of these elephants by poachers in search of the prized and valuable ivory tusks Secondly, many countries have banned the import of natural ivory, even if legally obtained, in hopes of curtailing the illegal poaching. It is clear that a substitute for the natural ivory is needed which simulates the desired characteristics of natural ivory, so as to eliminate the needless killing of the elephants while also providing an adequate substitute for the many items of commerce which require natural ivory.
Many substitutes have been proposed by the art to replace natural ivory. The prior art teaches that artificial ivory or ivory-like substances may be prepared from mineral fillers and various types of polymers. U.S. Pat. No. 4,508,575 to Oshima is an exemplary disclosure of an artificial ivory formed from a natural type polymer, like the protein casein, with a mineral filler. U.S. Pat. No. 3,443,261 to Battista et al. illustratively discloses the use of collagen, another natural type polymer, with a mineral filler for the formation of an ivory substitute. Lastly, cellulose, still another natural type polymer, has been used to make ivory-like piano keys, as disclosed in U.S. Pat. No. 4,840,104 to Ishida et al. Mineral fillers have also been used with other materials, such as nylon, plasticized amino resins, polyester resins and others, to form an ivory-like substitute. In addition, ivory-like substitutes have been formed using various ceramics without the addition of any other type of filler, and also various polymers acting alone.
As can be seen by the prior art, many attempts have been made to form a suitable ivory-like substitute. However, even though the prior art teaches the use of natural polymers, particularly the proteins, with a mineral filler for formation of an ivory substitute, there is no mention by the prior art of polyamino acids with a mineral filler for the formation of an ivory-like material.
Rather, this combination of materials, the polyamino acids and mineral fillers, has been taught for bone prothesis. Composite materials for bone prosthetics, which utilize polyamino acids with a mineral filler, are disclosed in U.S. Pat. No. 4,192,021 to Deibig et al. and U.S. Pat. Nos. 4,636,526, 4,698,375 and 4,842,604 to Dorman et al. These references all disclose the use of polyamino acids with mineral fillers, but for the preparation of bone-replacement prosthetic materials. These prosthetic materials are characterized by relatively high porosity, wherein the individual pores are also relatively large, and a high degree of biodegradability. Both of these features are required for bone prosthetics so as to promote and ensure tissue regrowth when the prosthetic is surgically implanted into a body.
Since bone and ivory share similar properties and common ingredients, namely collagen and hydroxyapatite, it would seem that the bone prosthetic material should have physical properties similar to a simulated ivory material. However, this is not the case. As stated above, bone prosthetics require a certain degree of porosity to function satisfactorily within the body. Porosity is not necessarily desirable within an ivory substitute, since the porosity would detract from the natural beauty of the ivory and would also make carving or other shaping of the ivory-like material more difficult. Therefore, even though they have a similar chemical make-up, in actuality, the bone prosthetics and the ivory-like materials are differentiated in nature and in their application. As an illustrative example, the present shortage of elephant ivory is not assuaged by the abundance of animal bones from animals of commerce.
Therefore, even though composite materials utilizing a mineral filler and polyamino acids may be utilized in the bone prosthetics art, these materials are characterized by properties which are substantially different than natural ivory and therefore are not suitable replacements for natural ivory. Accordingly, it would be desirable to provide a suitable replacement for natural ivory, such as wherein the replacement material is a composite consisting of a polyamino acid and a mineral filler. Further, it is desirable that such a composite material be manufactured without undue effort or difficulties, such as by using a facile, in-situ preparation method.